ABSTRACT The development of palygorskite rubber filler meets the rubber industry’s demand for a low-cost green filler, but the high cost of mineral purification and modifiers limits its industrialization. In an effort to decrease such expenses, this study opted for eco-friendly l-(+)-cysteine as the modifier for organic grafting on the surface of low-grade palygorskite ore. l-(+)-Cysteine–modified low-grade palygorskite rubber reinforcing filler (CYS@PAL) was successfully prepared through ultrafine ball milling and modification. Under the conditions that the modifier dose is 1 wt% and the filling amount of modified powder is 90 phr, the 100 and 300% constant tensile stress, tensile strength, and elongation at break of reinforced EPDM composite reached 4.07 MPa, 7.66 MPa, 24.78 MPa, and 764.70%, respectively. In addition, after thermo-oxidative aging at 70 °C for 48 h, the aging coefficient of the composite rubber reached 0.873. This work provides a low-cost and environmentally friendly method to prepare a high-performance low-grade palygorskite reinforcing filler.

ABSTRACT It is essential to achieve a strong interfacial interaction between the filler and polymer matrix for the production of polymer nanocomposites with superior performance. Ionic liquid (IL) 1-butylpyridinium bromide (BPB) was used for the surface modification of graphene nanoplatelets (GnPs). The modified GnP (PMG) was characterized using Fourier transformation infrared spectroscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy (TEM), and thermogravimetric analysis. BPB functioned as an intermediary between GnP and SBR via noncovalent interactions and promoted GnP dispersion in the SBR matrix. TEMs demonstrated that IL facilitates the homogeneous dispersion of PMG in the SBR/PMG nanocomposites. Dynamic mechanical analysis was used to understand viscoelastic behavior of the nanocomposites. The fraction of immobilized rubber chain around the PMG in the nanocomposites was obtained from the differential scanning calorimetric curve. The SBR nanocomposite prepared shows an improvement of 273% in tensile strength and 12.1 °C in degradation temperature.

ABSTRACT Natural latex gloves are prone to allergies and adhesion during use. Corn starch and talc, while improving adhesion, do not solve the allergy problem. These powders even increase allergy transmission pathways as well as create safety hazards such as granulomas. Depositing polymethylmethacrylate (PMMA)-chitosan (CS) on glove surfaces improves surface adhesion and does not become airborne like powders. However, the physical stability of the film formed by PMMA-CS deposition leaves much to be desired, and azobisisobutyronitrile (AIBN) and hexadecane present safety hazards. To ameliorate these problems, PMMA-CS was prepared by replacing AIBN and hexadecane with tween-80 and β-cyclodextrin, and PMMA-TOFA was prepared by using methyl methacrylate (MMA) and tall oil fatty acid (TOFA). The sulfur-prevulcanized natural rubber (SPNR) films deposited with PMMA-CS and PMMA-TOFA (PMMA CS/PMMA-TOFA/SPNR) had fewer safety hazards, higher roughness and physical stability. It is expected that PMMA emulsion can be applied to the inner and outer surfaces of medical gloves to reduce the safety hazards that exist in medical gloves.

ABSTRACT: Ethylene propylene diene rubber (EPDM) is the fourth most widely used general-purpose elastomer, accounting for about 10% of total synthetic rubber production. With its broad applications in the automotive and construction industries, the analysis of EPDM's dynamic viscoelastic properties is critical for optimizing product performance. While the effects of various fillers and their structures on EPDM's viscoelastic behavior have been widely studied, the impact of crosslink network architecture on long-term viscoelastic properties is seldom explored. To investigate the influence of different crosslink types and their compositions on the long-term viscoelastic behavior of EPDM, we have used thiol-amine analysis, time-temperature superposition for frequency-dependent properties, and temperature scanning stress relaxation. We establish correlations between crosslink features and the viscoelastic properties of carbon-black-filled EPDM. Additionally, we explore the effects of unique crosslink networks formed through hybrid cure systems containing accelerated sulfur and peroxide on the viscoelastic performance of EPDM. Our findings indicate that the frequency dependence of viscoelastic properties is governed by crosslink length, while temperature dependence is influenced by crosslink type. The results also indicated a strong correlation between plateau modulus and polysulfide crosslinks. These insights offer valuable guidance for optimizing the viscoelastic characteristics of next-generation elastomeric materials.

Abstract Fluorosilicone (FVMQ) rubber is commonly used in many military aircraft applications such as seals and gaskets due to its exceptional heat stability, low temperature flexibility and resistance to fuels and oil. In this investigation, a peroxide cured and silica filled FVMQ rubber compound was prepared and subsequently submitted to accelerated heat aging for up to 50 weeks at temperatures between 75 to 250°C. Heat aged samples were then tested for hardness, physical property characteristics and crosslink density by solvent swell and Double Quantum – Nuclear Magnetic Resonance (DQ NMR). The Arrhenius methodology was applied to the shifted experimental data assuming the principle of time-temperature superposition. The tensile strength and elongation at break both decrease upon thermal treatment. A small stiffness increase was observed by both the hardness and the tensile stress at 10% elongation test data. The characterization of the crosslink density by solvent swell testing was inconclusive. On the other hand, the DQ NMR testing clearly showed that the crosslink density decreases while the number of chain defects increases. The unaged crosslink distribution is heterogeneous in nature displaying much more heterogeneity than peroxide cured silicone. Non-linear Arrhenius behavior was observed between 75 to 250°C with a mechanism change at 175°C. The FVMQ crosslink distribution becomes more heterogeneous with aging. A significant loss of low molecular weight FVMQ due to depolymerization and backbiting reactions was observed at higher aging temperatures. Reactions with the silica surface also occurred with the creation of Si-O bonds. No direct evidence of thermo-oxidative and oxygenation reactions was observed. Reaction mechanisms have been proposed to explain the degradation of FVMQ due to heat aging.

ABSTRACT We describe a microcompounding method that can be used to characterize and compare cured small natural rubber samples. First, commercial Hevea and dried guayule (Parthenium argentatum) latex samples were microcompounded to validate the method. Latex was then extracted from the ground branches of six greenhouse shrubs of different ages and genotypes of wild type and transgenic guayule and coagulated into rubber samples. Size exclusion chromatography showed that the samples had different molecular weights and oligomer content. Little variation in physical properties was found between rubber extracted from shrubs of different age within a genotype, but a larger variation among genotypes was found. The new method allows testing of cured rubber samples from experimental variants and early screening out of genotypes to assess the impact of variations in cultivation practices or lab-scale processing conditions on rubber quality.

ABSTRACT The chemical resistance of HNBR and NBR in propylene is considered as no resistance by many chemical compatibility handbooks and industry chemical resistance tables and charts. This situation drives the change of the elastomer compounds from cheap HNBR/NBR to expensive fluoroelastomer for applications involving propylene. However, in the literature, NBR and HNBR are rated as having good or excellent chemical resistance to all other hydrocarbons, such as ethylene, ethane, propane, butane, and butylene. It seems that there are some special or unknown characteristics of propylene that make it very harsh to both NBR and HNBR; therefore, it is important to investigate the chemical resistance of NBR and HNBR in propylene. In this study, the chemical resistance of HNBR and NBR in propylene is investigated according to ISO 23936-2 and ASTM Standard D 471. The test results are crucial for the applications of HNBR/NBR in contact with propylene. Based on the tests, we investigated tensile property changes, volume changes, and glass transition temperatures and chemical structures of HNBR/NBR after aging in high-pressure propylene at an elevated temperature. The Hansen solubility parameters (HSPs) of HNBR and NBR and many hydrocarbons such as ethylene, ethane, propylene, propane, butane, and butylene were estimated. Based on the HSP, the polymer–solvent interaction parameters between HNBR/NBR and hydrocarbons were also estimated to explain the chemical resistance of HNBR/NBR in propylene. An aging mechanism was proposed to explain the changes of HNBR and NBR in propylene aging. This study enhanced guidance on chemical resistance of HNBR/NBR in propylene to the elastomer industry.

ABSTRACT The segregation of carbon black within a blend of NR/EPDM rubber at different mixing proportions (especially 70/30 and 30/70) was investigated via various microscopic techniques—transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM)-mapping, field emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM)—to analyze the characteristics of the rubber matrix from pristine rubber and final filled rubber blends. The investigation spans from the unfilled rubber to ultimate filled blends with low (25 phr) and high (50 phr) carbon black content. The use of OsO4 for selective chemical staining, in conjunction with microscopy, made it possible to distinctly understand each rubber phase within the blend, greatly aiding in the identification of filler migration to the preferred rubber phase. In addition, STEM-mapping confirmed the phase distribution by identifying the continuous and dispersed phases through precise detection and validation of the stained areas. The combined outcome of the microscopic studies (TEM, FESEM, and AFM) revealed that the carbon black filler is more inclined to move toward the unsaturated NR phase due to its active graphitic edges, making it more compatible with the NR phase, which has a higher degree of unsaturation than EPDM.

Abstract This study explores the deformation behavior of carbon black-filled elastomeric components under multiple cyclic loading conditions. Understanding the effects of repeated cyclic deformation is crucial for accurate Finite Element Method (FEM) simulations. We present an approach that captures both initial and subsequent cycles, converging to an equilibrium state. Experimental evidence from cyclic deformation and relaxation tests indicates that an equilibrium state is achieved within five deformation cycles. Our method analytically describes the relaxed or equilibrium state after multiple cyclic deformations by combining a relaxation model with a material model. We utilized a combination of a relaxation approach and the Modified Extended Tube Model (METM), allowing us to distinguish between polymer network effects and filler properties, thereby establishing a direct correlation between elastomer parameters and mechanical properties. The multiple cyclic deformation behavior can be analytically described using the Advanced Mullins Damage Modeling (AMDM) approach, validated through experimental data. The AMDM employs two damage functions for the increasing and decreasing stress phases of the cycle using the relaxed METM approach. The feasibility of this approach is demonstrated through 3D finite element (FE) simulations, confirming the validity of AMDM under cyclic deformation. The combination of the relaxed METM and AMDM approaches provides a robust framework for predicting the cyclic deformation behavior of filled elastomers, with significant applications in engineering and material science.